In the lawsuit, Patricia and Ronald Saylor accuse the defendants of negligence, violating Ethan Saylor's civil rights and violating the Americans with Disabilities Act.

"If any of the Defendants had heeded Mr. Saylor's aide as to how to deal with Mr. Saylor, his tragic and unnecessary death would have been avoided," they say. Saylor had Down syndrome and an IQ of about 40, they say, and it was easy to recognize his developmental disability.

The family is seeking an undetermined amount in compensatory and punitive damages, and is requesting a jury trial.

Saylor attended a screening of the movie "Zero Dark Thirty" on Jan. 12 with an aide. He became agitated after the movie and refused to leave. Three off-duty sheriff's deputies working as security officers handcuffed Saylor. The lawsuit says he "ended up on the floor."

According to the sheriff's office, Saylor suffered a "medical emergency." The deputies removed the handcuffs, attempted CPR and called for emergency workers, the sheriff's office said. Saylor died soon after.

A medical examiner ruled the death a homicide and found that Saylor died of positional asphyxia and excited delirium, complicated by his disability and weight. A grand jury later declined to indict the sheriff's deputies, and an internal investigation cleared them of wrongdoing.

Saylor's death drew national attention. In September, Gov. Martin O'Malley met with the Saylor family and said he would seek better training for law enforcement in how to respond when they encounter people with disabilities.

"That's a welcome step, but it does not look backward and say who's responsible and who should be accountable for what happened," said Joseph Espo, an attorney for the Saylors. "No one's been held accountable for Ethan's death."

The Saylors accuse the deputies — Richard Rochford, Scott Jewell and James Harris — of gross negligence and malice.

Daniel Karp, an attorney representing Frederick County, the sheriff's office and the three deputies, said the "extreme allegations" in the lawsuit were "disappointing."

"The allegations of deliberate wrongdoing are absolutely unwarranted," Karp said, referring to an internal sheriff's office investigation that the office declined to release. "The officers have been exonerated. An accident occurred, and the officers were not at fault."

Karp said many claims in the lawsuit are "exaggerated" or untrue, including an allegation that the deputies broke Saylor's larynx.

Petitions with more than 310,000 signatures were delivered to Gov. O'Malley asking for an independent investigation into the death of Ethan Saylor, a Frederick man with Down Syndrome. (Barbara Haddock Taylor/Baltimore Sun video)

National advocacy groups for people with Down syndrome are seeking an independent investigation into the January death of a Frederick County man after off-duty sheriff's deputies tried to remove him from a movie theater.